If you are a metalworker, a craftsman or an engine professional, precise measurements are your "daily bread". When measuring a cylindrical or spherical object, the best tool to use is undoubtedly the external micrometer. This well-calibrated tool is not very easy to use, but with patience and practice it will become an integral part of your skills.
Steps
Method 1 of 3: Measure
Step 1. Get familiar with the anatomy of a micrometer
Some parts are fixed, while others are mobile.
- Couple limitator;
- Graduated drum;
- Arched frame;
- Locking device;
- Measuring rod;
- Anvil;
- Graduated compass.
Step 2. Clean the anvil and measuring rod before starting
You can use a clean sheet of paper or a soft cloth by inserting it between the two elements of the instrument. Gently rotate the tool to close it, thus blocking the sheet or cloth; finally, gently pull the fabric or paper outward.
This step itself is not necessary for the measurement, but if you keep the rod and anvil surfaces clean, you will always have accurate readings
Step 3. Hold the object with your left hand and rest it against the anvil
This is a fixed element of the micrometer and can withstand more pressure than the measuring rod. Check that the object does not move and does not scratch the surface of the anvil.
Step 4. Hold the micrometer with your right hand
The headband frame should stay in the palm of your hand.
You can also attach the frame to a fixed vice, so you can use both hands throughout the process
Step 5. Rotate the friction limiter clockwise
Check that the 0 on the drum is aligned with the scale on the graduated compass.
Step 6. Rotate the limiter until the measuring rod touches the object
Apply some force, sometimes the drum makes a "click"; when you hear three "clicks" it's time to stop.
Step 7. Set the drum lock while the object is still in the micrometer
Although the lock is operated, the measuring rod can still move.
Step 8. Carefully extract the object
Be very careful not to scratch the surfaces of the anvil and movable rod, even the slightest scratch could interfere with the accuracy of the tool.
Step 9. Note the measurement value before unlocking the movable rod
If the latter has become loose, repeat the measurement.
Method 2 of 3: in Inches
Step 1. Recognize the different scales on the drum
- On the compass there is a scale with numbers indicating tenths of an inch (1/10) which in decimals is written 0, 100.
- Between these integers are three lines that each represent a quarter of a tenth of an inch, i.e. 0, 025.
- There are evenly spaced lines on the drum representing one thousandth of an inch, i.e. 0.001.
- Above the integer scale found on the compass are lines measuring one ten-thousandth of an inch, or 0, 0001.
Step 2. First read the whole number on the compass
The last visible number represents tenths of an inch. For example, if the last visible number is 5, it means that the object you are measuring is on the order of 5 tenths of an inch, i.e. 0.500.
Step 3. Count how many lines follow the integer
Multiply the number of lines by 0, 025 and you will know how many hundredths of an inch the object measures. In our case, 1 x 0, 025 is equal to 0, 025.
Step 4. Read the number on the drum scale and the corresponding notch closest to it, which is below the stock measurement line
If this is the closest line to the number 1, then the value will be 1 thousandth of an inch (0, 001).
Step 5. Add the three numbers together
In this case you will have 0, 500 + 0, 025 + 0, 001 = 0, 526.
Step 6. Turn the micrometer over and read the reference marks for the ten thousandths
Read the value that corresponds to the notch closest to the compass. If, for example, it were the line with the number 1, then your final reading would be 0.5261 of an inch.
Method 3 of 3: Metric Scale
Step 1. Recognize the different scales on the drum
- The scale on the compass typically has an upper line indicating millimeters and below this line are notches representing millimeters.
- The notches on the drum go up to 50 and typically each notch represents one hundredth of a millimeter (0.01mm).
- The horizontal lines above the compass scale measure thousandths of a millimeter, i.e. 0.001mm.
Step 2. First read the number of millimeters
The last line you could see indicated 5, so your object is on the order of 5mm.
Step 3. Add half millimeters to your measurement
If you can see only one notch, then the value is 0.5mm.
Don't just read the number you see near the notch, because the drum could be close to 50
Step 4. Find the hundredths of a millimeter value
If the line on the drum indicates 33, then the value is 0.33 mm.
Step 5. Add the line values together
As for our example, we have 5 + 0, 5 + 0, 33 i.e. 5, 83 mm.
Step 6. Add thousandths of a millimeter
If the mark of the thousandths shows the value 6, then it means 0, 006 mm. The object in our example measures 5.836 mm.
You should incorporate the thousandths of a millimeter value when the object has less resistance than the pressure applied by the micrometer
Advice
- Remember that an external micrometer, when used correctly, is much more accurate than a caliper.
- Practice, you need to develop a certain "feel" or "touch" in using this tool.
- Measure the object several times as a checkout procedure for your work.
- Reset the micrometer often to make sure the readings are correct.
- The instrument is very sensitive and must be stored at room temperature.
- When storing it, the anvil and the measuring rod should be separated, i.e. the micrometer should be left open, so temperature variations do not stress the instrument.
